tcpdemux.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 46 行

/* tcpdemux.c - tcpdemux */

#include <conf.h>
#include <kernel.h>
#include <network.h>

/*------------------------------------------------------------------------
 *  tcpdemux -  do TCP port demultiplexing
 *------------------------------------------------------------------------
 */
struct tcb *
tcpdemux(struct ep *pep)
{
	struct	ip	*pip = (struct ip *)pep->ep_data;
	struct	tcp	*ptcp = (struct tcp *)pip->ip_data;
	struct	tcb	*ptcb;
	int		tcbn, lstcbn;

	wait(tcps_tmutex);
	for (tcbn=0, lstcbn = -1; tcbn<Ntcp; ++tcbn) {
		if (tcbtab[tcbn].tcb_state == TCPS_FREE)
			continue;
		if (ptcp->tcp_dport == tcbtab[tcbn].tcb_lport &&
		    ptcp->tcp_sport == tcbtab[tcbn].tcb_rport &&
		    pip->ip_src == tcbtab[tcbn].tcb_rip &&
		    pip->ip_dst == tcbtab[tcbn].tcb_lip) {
			break;
		}
		if (tcbtab[tcbn].tcb_state == TCPS_LISTEN &&
		    ptcp->tcp_dport == tcbtab[tcbn].tcb_lport)
			lstcbn = tcbn;
	}
	if (tcbn >= Ntcp)
		if (ptcp->tcp_code & TCPF_SYN)
			tcbn =  lstcbn;
		else
			tcbn = -1;
	signal(tcps_tmutex);
	if (tcbn < 0)
		return 0;
	wait(tcbtab[tcbn].tcb_mutex);
	if (tcbtab[tcbn].tcb_state == TCPS_FREE)
		return 0;			/* OOPS! Lost it... */
	return &tcbtab[tcbn];
}